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Chromosome and granule movements in meiotic prophase and prometaphase have been studied by time-lapse cinemicrography in live spermatocytes of the house cricket, Acheta domesticus. Chromosome movements in prophase cells, up to one hour or more before breakdown of the nuclear envelope, are described. These movements are frequent but saltatory; are based mostly at chromosome ends but also at kinetochores; occur in very intimate association with the inside of the nuclear envelope; are directed towards and away from the extranuclear centres (centrioles); tend weakly to accumulate bivalents round the two centres and reach a velocity of 0.65 micron/sec. Saltatory movements in granules associated with extranuclear asters are remarkably similar to basic characteristics to the intranuclear chromosome movements. Surprisingly, the chromosome movements (and those granules) are reversably blocked by colcemid (but not lumi-colcemid), and yet occur in the apparent absence of an intranuclear envelope. However, kinetochore movements in very early prometaphase are similar in velocity and other respects to prophase movements; later prometaphase movements are clearly slower, and those of anaphase very much slower still. -The prophase movements suggest a two component model for motion: a non-microtubule, linear force producer together withrotubules with a skeletal, orientational role. Arguably, both these components are also necessary for chromosome movements in prometaphase and anaphase.

SYBENGA, J., and RICKARDS, G. K. 1987. The orientation of multivalents at meiotic metaphase I: a workshop report.Genome, 29: 6 12-620. During a workshop with 13 participants, several aspects of multivalent orientation at meiotic (pro)metaphase were discussed in an attempt to resolve some of the most prominent controversies with respect to terminology, interpretation of observations, and the validity of hypotheses and theories. For several terms and concepts, descriptive definitions were formulated that are recommended for general use. In the analysis of the behaviour of the multivalent in meiosis preprometaphase shape and position as important factors in final orientation were discussed, as well as the first contact between spindle and kinetochores and the role of reorientation. Specific characteristics of different multivalents and expected frequencies of different orientation types were considered. Finally, a few remarks on data collection and analytical procedures were made

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